Embedded GUI Glossary — All 33 Terms
Browse by letter group. Every term is cross-linked to the relevant Sparklet product or concept page.
Alpha Blending to CAN Bus / Chrom-ART
- Alpha Blending
- Alpha blending is the process of compositing two pixel layers using a transparency value (alpha channel). An alpha value of 0 means fully transparent; 255 means fully opaque. In embedded GUI, alpha blending is used for widget overlays, drop shadows, fade animations, and semi-transparent panels. Hardware accelerators such as DMA2D and D/AVE2D perform alpha blending off-CPU, significantly improving frame rate on MCUs.
- ASIL (Automotive Safety Integrity Level)
- ASIL is a four-level classification (A, B, C, D) defined by the ISO 26262 automotive functional safety standard. ASIL D is the highest level, applying to systems where failure could cause life-threatening harm without mitigation. Embedded instrument cluster GUI software typically operates at ASIL A or B. MISRA C compliance is a prerequisite at all ASIL levels.
- Bare Metal
- Bare metal refers to running firmware directly on microcontroller hardware with no operating system layer. There is no scheduler, no task management, and no kernel — the application runs in a single super-loop or interrupt-driven model. Bare metal deployments offer the lowest latency and smallest memory overhead, common in cost-sensitive or power-constrained products. Sparklet supports bare-metal deployment; the render loop integrates directly into the application super-loop.
- BusyIndicator
- BusyIndicator is a Sparklet widget that displays an animated spinner while a background task is running — for example, while loading sensor data or completing a calibration routine. The widget animates until explicitly stopped via API. BusyIndicator integrates with Sparklet's dirty-region rendering so that only the indicator's bounding box is redrawn per frame, minimising CPU overhead.
- CAN Bus (Controller Area Network)
- CAN bus is a serial communication standard for multi-node communication in automotive and industrial systems. In embedded instrument clusters, CAN frames carry vehicle data — speed, RPM, fuel level, battery voltage, warning flags — from powertrain ECUs to the display MCU. The display MCU parses incoming CAN frames and maps values to Sparklet widget properties (Meter value, Graph data point, warning icon visibility) via the application layer.
- Chrom-ART / DMA2D
- Chrom-ART Accelerator (ST's name for DMA2D) is the STM32 2D DMA hardware unit that offloads pixel copy, fill, alpha blending, and colour format conversion from the Cortex-M CPU. The CPU sets up a transfer descriptor and DMA2D completes the operation independently, freeing the CPU for application logic. DMA2D is a key hardware acceleration component for Sparklet on STM32 H7, F7, and F4 MCUs, enabling smooth 60 fps UI without an external GPU.
D/AVE2D to HMI / HSM
- D/AVE2D (Dave2D)
- D/AVE2D is a dedicated 2D vector and raster GPU integrated in Renesas RH850 and RA series MCUs. It supports anti-aliased line and shape rendering, gradient fills, hardware-accelerated glyph drawing, and alpha blending — all without CPU involvement. On Renesas platforms, Sparklet's GDI layer routes rendering primitives to D/AVE2D hardware, enabling smooth anti-aliased instrument cluster graphics at automotive-grade frame rates.
- Dirty Region
- A dirty region is a portion of the display whose pixel content has changed since the last frame and needs to be redrawn. Dirty-region (partial) rendering tracks which rectangular areas of the screen have been invalidated by widget state changes and redraws only those areas. This significantly reduces CPU and GPU workload in UIs with mostly static content. Sparklet implements dirty-region tracking automatically — application code does not need to manage it explicitly.
- Embedded GUI
- An embedded GUI is a graphical user interface designed and optimised for deployment on microcontrollers (MCUs) and microprocessors (MPUs) in embedded systems. Unlike desktop GUI frameworks, embedded GUIs must operate within kilobytes of RAM, produce deterministic rendering timing compatible with RTOS scheduling, and run on display hardware without a desktop OS or window manager. Sparklet is an embedded GUI framework built from the ground up for embedded constraints.
- Flint UI Designer
- Flint UI Designer is Sparklet's PC-based WYSIWYG drag-and-drop GUI design tool. Engineers and designers use Flint to place widgets on a canvas, configure properties, wire state machine transitions, define animations, and import image assets. With a single click, Flint exports optimised, platform-agnostic C code that integrates directly into the Sparklet application layer — no manual UI code required. See the Flint UI Designer page for full feature detail.
- Framebuffer
- A framebuffer is a region of RAM that holds the pixel values for the current display frame. The display controller reads the framebuffer and outputs the corresponding video signal. Framebuffer size is determined by resolution and colour depth: a 480×272 display at 16-bit colour requires 261 KB of RAM for a single full-screen buffer. For memory-constrained MCUs, Sparklet supports partial-buffer rendering — holding only a scan-line-sized buffer in RAM and flushing it progressively, eliminating the need for a full-resolution framebuffer.
- GDI (Graphics Device Interface)
- The GDI is the rendering abstraction layer in Sparklet's seven-layer architecture. It sits between the widget layer (which issues draw commands) and the HAL layer (which executes them on hardware). The GDI provides uniform drawing primitives — fill rectangle, blit image, draw line, render text glyph — that map to software implementations on basic MCUs or hardware acceleration calls on supported platforms. Widget code is identical regardless of whether the target MCU has DMA2D, D/AVE2D, Mali GPU, or no accelerator.
- HAL (Hardware Abstraction Layer)
- The HAL is the lowest layer in Sparklet's architecture — the platform-specific code connecting the framework to a particular MCU or MPU board. It contains the display driver, touch controller driver, system timer, and GPU integration hooks. Porting Sparklet to new hardware primarily means implementing the HAL for that platform. Sparklet ships with reference HAL implementations for all supported platforms.
- HMI (Human-Machine Interface)
- An HMI is the interface through which a human operator interacts with a machine or system. In embedded systems, an HMI typically comprises a display panel, a touch input layer, and sometimes physical buttons or rotary encoders. The term HMI is used broadly across automotive, industrial, medical, and home automation. Sparklet provides the embedded GUI framework layer within an HMI product — rendering the visual interface and handling touch and button events.
- HSM (Hierarchical State Machine)
- A hierarchical state machine (HSM) is a state machine architecture where states can be nested — child states inherit event handling from their parent state. This allows complex behavioural logic to be expressed more compactly than a flat state machine. Sparklet uses an HSM in its RS_MIN layer to implement screen navigation, modal dialog logic, and event-driven UI behaviour. Flint UI Designer provides a visual UML-style state machine editor that generates the HSM implementation in C automatically.
IEC Standards to MPU
- IEC 61508
- IEC 61508 is the foundational international functional safety standard for electrical, electronic, and programmable electronic safety-related systems. It defines four Safety Integrity Levels (SIL 1–4) and specifies software development requirements at each level, including the use of structured coding standards such as MISRA C. IEC 61508 underpins domain-specific safety standards including ISO 26262 (automotive) and IEC 62304 (medical devices).
- IEC 62304
- IEC 62304 is the international standard for medical device software lifecycle processes. It defines three software safety classes — Class A (no injury risk), Class B (non-serious injury risk), and Class C (serious injury or death risk) — each with progressively stricter development and documentation requirements. For Class B and C software, IEC 62304 requires SOUP documentation for any third-party library, including embedded GUI frameworks. Sparklet's MISRA C source compliance and documented architecture support this process.
- ISO 26262
- ISO 26262 is the automotive functional safety standard applicable to road vehicles. It defines ASIL A through ASIL D safety classification for safety-related electrical and electronic systems. Part 6 specifies software development requirements including MISRA C compliance for safety-critical code. Embedded instrument cluster and HMI display software typically operates at ASIL A or ASIL B. See the safety-critical HMI page for how Sparklet supports ISO 26262 programmes.
- LVDS (Low Voltage Differential Signalling)
- LVDS is a differential electrical signalling standard used to connect MCUs and MPUs to medium and large TFT display panels (typically 7"–15"). The differential pair design provides noise immunity over cable runs, making LVDS common in industrial open-frame panels, medical monitors, and automotive head units where the display is mounted remotely from the main PCB. MPUs running Linux (NXP i.MX 8, Rockchip) often have native LVDS or dual-LVDS output.
- Mali GPU
- Mali is a family of graphics processing units designed by ARM and licensed to silicon vendors. In the embedded MCU/MPU space, Mali GPUs appear in Renesas RA8D1 (Mali-Limav variant) and NXP i.MX 8 (Mali-G31). The Mali GPU supports OpenGL ES 2.0 and Vulkan, enabling hardware-accelerated 3D rendering and hardware layer composition. Sparklet's 3D rendering layer uses OpenGL ES when a Mali GPU is available, enabling the 3DWidget and 3DView components to render imported .obj and .fbx models at full frame rate.
- MCU (Microcontroller Unit)
- An MCU is a single-chip integrated circuit combining a CPU core, RAM, flash memory, and peripherals on a single die. Most embedded GUI MCUs are ARM Cortex-M class (M0+ through M7) operating at 64–800 MHz with 256 KB to 2 MB of RAM. MCUs differ from MPUs in that they run firmware directly (bare metal or RTOS) without a full operating system. Sparklet's minimum RAM footprint of 16 KB makes it deployable on the most memory-constrained Cortex-M0+ class MCUs.
- MIPI DSI (Display Serial Interface)
- MIPI DSI is a high-speed differential serial interface standard for connecting processors to display panels. It uses 1–4 differential data lanes plus a clock lane, supporting data rates of up to 2.5 Gbps per lane. MIPI DSI requires fewer PCB traces than parallel RGB and supports longer cable runs, making it the preferred interface for modern OLED displays and high-resolution TFT panels. Supported on NXP i.MX RT1170, NXP i.MX 8, Renesas RA8D1, and Rockchip RK3506G2.
- MISRA C
- MISRA C is a set of C language coding guidelines published by the Motor Industry Software Reliability Association. It restricts unsafe C constructs including dynamic memory allocation, recursion, implicit type conversions, and multiple return points. MISRA C compliance is mandatory for safety-critical embedded software in automotive (ISO 26262), medical (IEC 62304), and industrial (IEC 61508) applications. Sparklet is developed to MISRA C guidelines throughout.
- MPU (Microprocessor Unit)
- An MPU is an application-class processor (typically ARM Cortex-A series) that runs a full operating system such as Embedded Linux, Android AOSP, or QNX. MPUs have larger memory buses, external DRAM (hundreds of megabytes), hardware MMUs, and GPU subsystems — enabling complex embedded displays with video decode, 3D graphics, and multi-application environments. Sparklet supports MPU-class platforms including NXP i.MX 8 and Rockchip RK3506G2, using OpenGL ES and Vulkan for hardware-accelerated 3D rendering.
OTA to SIL
- OTA (Over-the-Air Update)
- OTA update is the mechanism for delivering new firmware or software to a deployed embedded device remotely, over a wireless or wired network channel. For embedded GUI products, OTA typically delivers an updated UI binary — new screens, updated widget layouts, or revised animations — independently from the underlying firmware. Separating the UI binary from the firmware binary (enabled by Sparklet's layered architecture) means UI updates can be validated and deployed without a full firmware reflash, reducing the risk and cost of field updates.
- Partial Buffer Rendering
- Partial buffer rendering is a Sparklet rendering mode in which only a fraction of the display's pixel data — typically a small number of scan lines — is held in RAM at any one time. Sparklet renders into this small buffer and flushes it to the display controller progressively until the full frame has been output. This eliminates the need for a full-screen framebuffer in RAM — reducing the memory cost of a 480×272 display from 261 KB to as little as a few kilobytes. Essential for SPI-connected OLED displays on wearable MCUs.
- ProgressBar
- ProgressBar is a Sparklet widget for displaying the progress of a value or task relative to a defined range. It supports horizontal, vertical, and circular (ring/arc) variants. The fill level is set via API and can be animated — Sparklet interpolates from the current value to the target over a configurable animation duration. ProgressBar is commonly used in medical devices (dose delivery), industrial HMI (batch completion, tank fill level), and consumer appliances (programme progress, battery charge).
- Royalty-Free
- Royalty-free is a software licensing model in which the licensee pays a one-time or periodic fee — typically per developer seat — with no additional per-unit payment for each device manufactured or shipped. This contrasts with royalty-bearing models where the vendor charges a fee for each unit sold. Sparklet uses a royalty-free developer-seat model: you pay for the engineers using the framework, not for the devices deployed.
- RTOS (Real-Time Operating System)
- An RTOS is an operating system designed to provide deterministic, time-bounded task scheduling. Tasks are assigned priorities and time budgets; the scheduler guarantees that a high-priority task will preempt lower-priority tasks within a defined worst-case latency. RTOS is essential in embedded systems where display updates, sensor reads, communication protocol handling, and safety monitors must all run concurrently with predictable timing. Sparklet supports FreeRTOS, Azure RTOS (ThreadX), Zephyr, QNX, and ITRON, as well as bare-metal super-loop deployment.
- RTL (Right-to-Left)
- RTL refers to the text rendering direction used for Arabic, Hebrew, Farsi, and Urdu scripts — where characters are written and read from right to left. Implementing RTL in embedded GUI requires both reversing the text rendering direction and applying Unicode character shaping. Flint UI Designer pre-shapes Arabic text at design time using Unicode Presentation Forms (U+FE70–U+FEFF), so the MCU receives pre-shaped glyph sequences and only needs to render them right-to-left — avoiding the need for a runtime shaping library on the MCU.
- SIL (Safety Integrity Level)
- SIL is the safety classification system defined by IEC 61508 for industrial electrical and electronic safety-related systems. There are four levels (SIL 1 through SIL 4), with SIL 4 representing the most stringent requirements. SIL is the industrial equivalent of the automotive ASIL classification. Most industrial operator panels and process HMI displays target SIL 1 or SIL 2, which requires structured software development processes including static analysis, code review, and the use of MISRA C-compliant libraries.
Widget and WYSIWYG
- Widget
- A widget is a pre-built, reusable UI component in an embedded GUI framework. Each widget encapsulates its own rendering logic, event handling (touch, key input), and state management. Application code interacts with widgets through a defined API — setting a Meter value, pushing data to a Graph, changing a Button state — without managing any drawing primitives directly. Sparklet provides 36+ widgets including Button, Graph, Meter, Slider, ProgressBar, Carousel, Clock, DatePicker, ListBox, and 3DWidget. Widgets are the primary productivity multiplier of a GUI framework: instead of drawing a gauge from scratch, you configure a Meter widget with a few API calls.
- WYSIWYG (What You See Is What You Get)
- WYSIWYG describes a design tool paradigm in which the editor shows the exact output that the system will produce. In embedded GUI, a WYSIWYG design tool renders the display canvas at the same resolution, colour depth, and layout as the target embedded display. Flint UI Designer is a WYSIWYG tool: the Flint canvas matches the final embedded display appearance, including widget sizes, font rendering, image assets, and animation behaviour. Designers can validate the UI appearance without deploying to hardware, and engineers can review the generated C code knowing it precisely matches the design intent.